


The Learning Curve

by sindontquit



Category: Undertale
Genre: Ecto-Vagina (Undertale), Fluff and Smut, M/M, Oral Sex
Language: English
Status: Completed
Published: 2017-06-07
Updated: 2017-06-07
Packaged: 2018-11-10 11:29:16
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,286
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11126136
Author URL: https://archiveofourown.org/users/sindontquit/pseuds/sindontquit
Summary: The skelebros only admitted their feelings to each other a few weeks ago. Papyrus REALLY liked what Sans did to him last night. Now he wants to reciprocate.Just some fun, fluffy PWP in which Papyrus learns how to give head.





	The Learning Curve

**Author's Note:**

> Communication is key, kids.
> 
> (I just liked that alliteration. Don't read this if you're actually a kid.)

There was a soft knock at Sans' bedroom door.

The reclining skeleton went up to his elbows on the bed, setting his book aside. "Come on in, Paps," he called. Papyrus opened the door and smiled shyly at his brother from the doorway. 

"What's up, bro?" Sans sat the rest of the way up and patted the mattress next to him. Papyrus' cheekbones tinted slightly orange, but he came over and sat next to his smaller brother. He seemed not to know what to do with his hands, alternately fiddling with his gloves and tapping his phalanges against the sheets. He was also avoiding Sans' eyes.

Sans grinned a little wider. His brother was so cute like this. It had only been a few weeks since they had admitted their feelings for one another, and while they had agreed to take things slow, Papyrus still seemed to be a little shy when he was close to Sans. Sans had no reservations about exploiting his brother's adorable nervousness. 

The smaller skeleton reached up and gently ran his phalanges down his brother's arm before slipping them under Papyrus' chin to tip it up gently. Sans caught his brother's gaze and held it. "Something you want, Paps?" he practically purred.  
Papyrus flushed a deep orange. "YES, ACTUALLY, THERE IS."  
Sans resumed trailing his hands up and down the larger skeleton's arm. "Mhm," he murmured. "Go on."  
Papyrus looked at his gloved hands. "IT'S ABOUT... LAST NIGHT... THAT THING YOU DID. WITH YOUR TONGUE."  
Sans' hand stilled and immediately his full attention was on his brother's face. Oh god. He'd done something wrong. What had he done?  
His soul constricting, Sans tried his best to keep his features composed. "What--" he cleared his nonexistent throat. "What about it, Paps?"  
Papyrus looked up at Sans and immediately scooted closer, taking his hand. "NOTHING BAD!" he said, looking down reassuringly into his brother's eyelights. "I LIKED IT!"  
Man, Sans couldn't get anything past Papyrus. His grin relaxed, and he squeezed the taller skeleton's hand.  
"Good. Then what's up?"  
"WELL... I REALLY, REALLY LIKED IT. I... WANT TO DO IT TO YOU."  
"Oh."  
It was Sans' turn to blush, which he did, somewhat furiously.  
Papyrus leaned closer. "I WANT TO MAKE YOU FEEL THAT GOOD, BROTHER," he said, placing his own hand on Sans' femur. "BUT... I AM CONCERNED THAT I DON'T KNOW HOW. THE GREAT PAPYRUS ALWAYS WANTS TO LEARN AND DO THE BEST JOB HE CAN, SO.... WILL YOU SHOW ME HOW TO DO IT CORRECTLY?"

Sans’ soul started to beat faster as his brother held his gaze. "Y-yeah, of course, bro."  
Papyrus smiled and shifted to his knees, placing a hand gently on Sans' ribcage.  
"Whoah, wait, Paps... did you mean, like... right now?"  
"YES, SANS."

Papyrus advanced further, pushing until the smaller was flat on his back, a blue glow growing increasingly bright from his face and pelvis.  
Sans gasped as Papyrus pinned him to the mattress. The taller skeleton's glowing orange tongue appeared in his mouth, and he began licking at Sans' cervical vertebrae.  
Sans squirmed beneath him, trying to put a coherent thought together. Paps was being so aggressive...  
He liked it.  
He summoned his own blue tongue and began to tangle it with his brother's in earnest, small sparks of magic erupting from their contact like pleasurable static charge. They both moaned into the kiss. Papyrus rolled his hips against the smaller skeleton's, returning his attentions to Sans' neck. Sans wrapped his arms around his brother's shoulders, arching into him. Fuck, this felt good. Why had they waited so long?

Papyrus broke the kiss, staring down at Sans and gasping in air he didn't need. Sans' sockets were hazy and half-lidded as he looked up into his brother's face. Papyrus' hands began to creep under his brother's soft t-shirt.  
"So... mmh... you want to eat my pussy, huh?"  
Papyrus' face ran through a delightful series of expressions, torn between his embarrassment at the lewd language and the fact that Sans was absolutely correct.  
He settled for nipping at Sans' collarbone. "YES," he said, muffled against Sans' neck. "I DO."  
“Well, you’re… ah... doing great so far.” Papyrus hummed in a pleased sort of way, his hands pushing Sans t-shirt up further. He pressed his teeth against the sensitive ribs, nibbling gently and soothing the bites with his tongue. A blue glow was growing along Sans’ joints, shifting as the smaller skeleton arched into the touch. “Mmmm…. Paps... “ Sans didn’t try to direct his brother through this part. Papyrus had proven himself dedicated and creative at working Sans up… as though the mere thought that his brother’s hands were finally on him wasn’t enough to get him going.  
Papyrus lowered his head into the spot where Sans’ ribs converged and licked gently at the underside of his brother’s sternum.

“Aaah!” Sans cried out, throwing his head back in surprised pleasure. His hips bucked unconsciously, and Papyrus grinned up at him. 

“Do… do my spine next… on the inside…” Sans said breathlessly, lowering his eyes back to Papyrus’ ministrations.

Papyrus lowered his head further, tilting it and carefully maneuvering his skull into Sans’ ribcage. It only really fit his face, but he extended his tongue up to the highest vertebrae he could reach. He flexed and swirled his tongue around the joints, the way Sans had done to him in very recent memory. His own orange magic swelled at the thought.

Sans’ phalanges fisted hard in the sheets, and he grit his teeth as he held himself still, trying not to make things harder (heh) for the younger skeleton. Low whines escaped through his teeth. He stared hungrily down at his brother’s glowing sacrum, lifted and exposed in that position. Papyrus backed slowly out of Sans’ ribcage, his orange tongue lapping at lower and lower vertebrae. Finally, he opened his mouth wide and bit down on the lowest disks. 

“Fuck!” Blue magic flared, and Sans’ pussy manifested. Papyrus sat back on his knees and stared down at it, his expression equal parts eager and nervous. He ran his phalanges tentatively over the glowing construct, feeling the heat of it. Sans sucked in a breath at the light touch, then chuckled fondly at his brother. “Scared it’ll bite ya?”  
Nervousness suddenly won out on Papyrus’ face, and he pulled his hand back. “THEY… THEY CAN’T ACTUALLY DO THAT, RIGHT?”

Sans stared at his brother for a long moment before both of his hands flew up to cover his face, shoulders shaking with barely suppressed laughter. A few snorts came through anyway. Papyrus was unamused. “SANS! DON’T LAUGH AT ME! IT WAS AN HONEST QUESTION!”  
“Oh… I know, bro. I know.” Sans wiped a tear from his eye, trying to be discreet. He failed, and Papyrus glared down at him. “No, they can’t actually do that.” A fresh round of giggles overcame him and he brought one hand up to cover his mouth. 

“HEY! DO YOU WANT ME TO DO THIS OR NOT?”

The insistent throb of Sans’ pussy was suddenly much stronger than his desire to laugh. “Yeah, bro.... Sorry.” Sans lay back, grinning, and tilted his pelvis up towards his brother. Although he still looked disgruntled, Papyrus reached down and began to stroke it gently. Sans’ breaths became harsher, his femurs spreading to allow his brother better access. “Uhn… so… j-just… touch it with your hands first…” 

Papyrus slid his phalanges along the soft folds, feeling slick magic on his bones as he moved them near Sans’ entrance. He remembered what Sans had done when he’d reached this point. Pulling back slightly, he locked eyes with his brother, raised his phalanges to his mouth, and gave them a long, languid lick. Sans groaned. “Shit… Paps…” 

Papyrus returned his attention to Sans’ pussy. It was hot under his touch, practically begging for more stimulation. As if to prove this thought correct, Sans rocked up against his fingers. “Okay, so,” Sans panted, “you see my clit?” 

Papyrus did see it. In fact, the sight of it was heating his own magic rapidly. “Take… your thumb… and rub circles around it. Don’t touch it directly yet.” Papyrus did as he was told, circling Sans’ clit and basking in the moans he elicited. Sans’ femurs began to tremble, and the younger skeleton rubbed soothingly along his legs with his free hand. “Yes,” Sans gasped. “Touch me other places too… when you ca--MMM! Fuuuuck...!” Papyrus had leaned in and licked, long and slow, along the femur without breaking the pace of his hand against Sans’ pussy. 

Sans wasn’t used to his brother being so quiet. Usually when Papyrus learned a new skill, he asked a million questions, loudly and enthusiastically. Now, however, he seemed intensely focused on both listening to Sans’ verbal directions and picking up the unconscious cues of his body. His brother really was the best.  
“You can press a little harder now… a little lower… that’s it. Oh fuck, Paps, that feels amazing. You’re doing so well.”

“OF COURSE I AM! I AM A VERY FAST LEARNER AFTER ALL!” Papyrus’ grin was shy and pleased despite his bravado. “I WANT TO USE MY TONGUE… CAN I?” 

“Yeah, go ahead, bro. Um… start out pretty soft… I’ll tell you when you can go harder. And at the… end… you can suck on it. But move your tongue against the bottom of it too. Like this.” Sans took Papyrus’ hand and sucked on a fingertip, brushing his magic softly against the underside. Papyrus shivered. “WOWIE… IS THAT WHAT YOU DID TO ME?” Sans nodded with his mouth still wrapped around his brother’s phalange. He released it, but held onto Papyrus’ hand with his own, licking gently where Papyrus’ hand met his wrist. Papyrus shivered again. “OOOH… THAT FEELS NICE…” Sans tugged him closer, now licking at the spot where his humerus met the bones of his forearm. “MMM…” 

“Paps…” Sans breathed, reaching up to bring their skulls together. The magic of their tongues slid against one another, the slowness of the kiss generating a pulsing heat like glowing coals. 

Papyrus broke the kiss, searching Sans’ eyes. His brother nodded. “Oh! Last thing… don’t stop when I come. Keep going until I push your head away myself.”  
The taller skeleton nodded, eyes gleaming in anticipation. He scooted back on the mattress and lowered his mouth towards the hot blue flesh of Sans’ pussy. He lapped at it experimentally. 

Sans bucked and hissed through his teeth, head lolling to the side as his mouth fell open. His brother’s tongue felt so good, warm and slick and... oh, fuck, it was so good. 

Papyrus too was lost in the sensation of Sans’ soft magic pressed up against his face. Everything was wet and blue and he loved it. The thought that he was finally doing this to his older brother sent thrills of pleasure down his spine. Every sound Sans made was because of him. Every gasp and moan and tremble. His. He moaned into Sans’ pussy. 

Sans felt the vibrations and clung desperately to the sheets as Papyrus mimicked the motion of his fingers with his tongue. The orange construct swirled around his clit, Papyrus’ hands climbing up Sans’ ribcage to stroke at the thin bones. Sans was gasping. “F-flatten your tongue out… move your head instead to make the circles. That’s it… oh fuck paps yes right fucking there just like that--!”  
Sans’ ribcage was heaving, his arms thrown out to either side and his legs clenching around his brother’s head. Papyrus moaned again as Sans started to roll his hips deliriously against his face. He remembered something Sans had done to him and began to shake his head back and forth, dragging his tongue, never breaking contact with his clit. Sans’ desperate moans grew louder and louder, his femurs shaking against the sides of Papyrus’ skull. 

“Ofuckpapsdontstoppleasepleasepleasefuckmoreineedmoreimsofuckingclose--”

Papyrus took his brother’s clit in his mouth and sucked, tonguing the bottom as he’d been shown. 

Sans went rigid, head thrown back, mouth wide open in a silent scream. Papyrus felt his pussy clench, hard, for several long moments before it began to flex and relax repeatedly against his tongue. The toes of Sans’ feet, pressed into the back of Papyrus’ ribcage, curled and relaxed again and again in time with the contractions. Sans released the broken cry he’d been holding, melting into short, panting moans. Papyrus released his brother’s clit and instead resumed the softer, massaging circles, staring up at Sans’ face. It was flushed as blue as his pelvis, his mouth still hanging open. Sans slowly brought his hand up to cover it, muffling the sounds of his aftershocks. 

“Mmf… mmf… mmf… mmf… mmf… mmmmmmmmmm. Fuck, Paps.” The smaller skeleton reached down and lifted Papyrus’ head, tugging him up over his own body. He smirked lazily up at his brother and ran his tongue through the mess on Papyrus’ face, lapping at his own blue cum. Papyrus groaned weakly, the action so unexpectedly erotic that his knees nearly gave out. “OH… SANS… F-FUCK…”

Sans pulled back in shock. “Did you just swear?”  
“...NO?”  
Sans laughed, the sound melting into a satisfied sigh.  
“Goddamn, bro. That was incredible.”  
“FOR ME TOO. YOU’RE SO BEAUTIFUL, SANS.”  
“Mmm. You too, Paps. Thank you for that.”  
“IT WAS MY PLEASURE.”

The brothers simply lay together for a few moments, stroking each other softly.  
Sans started to sit up.  
“WHERE ARE YOU GOING?”  
“Glass of water.” Sans tested his weight on his weakened legs and grinned. “Assuming I can stand. And when I come back...”  
He looked down at his brother, still on the bed, and his grin widened.  
“...I’m gonna make you swear some more.”


End file.
